With an integration of the optical technology for photograph and the digital electronic technology recently, camera phones, small digital cameras or miniature home video cameras become available in the market for modern people's works or lives. Optical lens, which are the key components of this kind of production, not only have to be miniature and light, but also have to satisfy the demands for the high zooming rate and the high resolution. Generally, a lens system for those optical devices comprises multiple lens groups, a plurality of lens or longer length for possessing a high zooming rate. Meanwhile, the lens having high zooming rate will comprise a specific low chromatic dispersion lens and an aspherical lens to reach the demands for the resolution.
In a zoom lens, it will be necessary to appropriately construct the constitution of lens in each lens group to not just seek the miniaturization of the camera lens but to obtain the expecting zooming rate at the same time. If the powers of all lens groups are increased, the moving interval of each lenses group can be decreased during a zooming action for shortening the length of the whole camera lens. However, with the increase in the power of each lens group, a problem that the aberration fluctuates with a longer zoom and is difficult to correct properly may raise. Therefore, with regard to a miniature zoom lens, it is truly a dilemma of maintaining the high optical function of the zoom lens and simplifying the constitution of the optical system as possible to a designer of a zoom lens.
In this technique field, many resolutions of miniature zoom lenses have been disclosed, such as U.S. Pat. No. 5,185,678 of Minolta, issued in Feb. 9, 1993, and JP Patent No. 3044757 corresponding to the aforesaid US Patent. The Patent disclosed a zoom lens having five lens groups. These five lenses groups are first lens group with positive power, second lens group with negative power, third lens group with positive power, fourth lens group with positive power, and fifth lens group with positive power in order from the object side to the image side. Each lens group includes several single lenses or compound lenses. The whole camera lens includes about 16 to 20 pieces of optical lenses totally. Moreover, U.S. Pat. No. 6,061,186 of Canon, issued in May 9, 2000, also disclosed a zoom lens having five lens groups with positive power, negative power, positive power, positive power, and negative power in order respectively. The focal length of the zoom lens can be adjusted from a wide status to a telephoto status by changing respective intervals between lens groups. The lens groups of the zoom lens also include several single lenses or compound lenses. The whole camera lens includes about 17 to 19 pieces of optical lenses totally. The lenses employed in zoom lenses according to the prior arts are over 16 pieces. Except the increased cost of the camera lens, overweight of such zoom lenses is one of drawbacks either.
Consequently, there is a need to develop a light zoom lens, which is small, comparatively simplified, and still with excellent optical function.